1. Field of the Invention
The present invention relates to a motion reduced floating structure which has an L-type wave damping structure for motion reduction.
2. Description of the Related Art
A floating structure is known as a building for effective use of marine. In a ship to transport persons and goods, fuel cost reduction is a higher priority than prevention of a rotational motion and a translational motion. For this reason, a hemispherical structure is adopted as a bow shape to reduce wave resistance. In the floating structure which is moored at a predetermined position, the prevention of the motions on the horizontal plane is important. The motions on the horizontal plane are such as a translational motion in a horizontal direction, a rotation motion around a horizontal axis and a drift motion.
It is known in Japanese Laid Open Patent Application (JP-P2000-135999A) to attach a wave damping structure on the longer side portions of the floating structure. The wave damping structure has so-called L-type structure in which a vertical member extends from the longer side portion of the floating structure and a horizontal member extends from the end portion of the vertical member in the horizontal direction under the seawater surface. Thus, it is possible for the wave damping structure to reflect wave effectively. However, when the wave damping structure reflects the wave, the floating structure receives reaction force and the horizontal momentum of the floating structure changes largely. Thus, over-prevention of the motions on the horizontal plane degrades the mooring performance of the floating structure.
The motion prevention effect of the floating structure becomes effective if the wave damping structure is formed long into a direction orthogonal to a wave progress direction when the wavelength of the wave is long. Supposing that a horizontal board is in the bottom of the sea and that the wavelength is 200 m, the horizontal board length of 20 m is needed which is the length of {fraction (1/10)} of the wavelength at least. The wave damping structure needs to be formed long irrespective of whether the floating structure is small or large. Therefore, the wave damping structure itself becomes large and makes mass large.
In the floating structure in which habitability and workability are important, the prevention of the motion around the horizontal axis is important primarily and the reduction of the translational motion in the horizontal direction is important secondarily. Both of the translational motion in the horizontal direction and the rotational motion around the horizontal axis depend on a wave period.
Also, there is a case that the translational motion becomes large when the rotation motion is suppressed. Therefore, it is important that the translational motion in the horizontal direction and the rotational motion around the horizontal axis are balanced, taking the wave period into account.
When it is planned to install the wave damping structure in an existing floating structure or an existing work ship, it is desirable that the wave damping structure is small and light in weight and that the structure is reinforced.
Therefore, an object of the present invention is to provide a motion reduced floating structure in which motions on a horizontal plane can be prevented.
Another object of the present invention is to provide a motion reduced floating structure, in which the prevention of the rotational motion around the horizontal axis and the prevention of the translational motion in the horizontal direction are balanced.
Another object of the present invention is to provide a motion reduced floating structure, which is small and light.
Another object of the present invention is to provide a motion reduced floating structure whose structure is reinforced.
In an aspect of the present invention, a motion reduced floating structure, includes a main hull structure and a wave damping structure connected with the main hull structure. The wave damping structure may include a back board, a lower horizontal board and vertical members. The back board is connected with the main hull structure, and the lower horizontal board is connected with a lower portion of the back board to extend in a horizontal direction and is under a seawater surface in case of mooring. The vertical members are connected with the lower horizontal board and the back board. A vertical direction hole is provided for the lower horizontal board.
Here, each of the vertical members may be formed of a triangular board to enforce the lower horizontal board and the back board.
The wave damping structure is provided for a portion of the main hull structure which receives wave.
In another aspect of the present invention, a motion reduced floating structure includes a main hull structure and a wave damping structure connected with the main hull structure. The wave damping structure includes a back board, an upper horizontal board, a lower horizontal board, and vertical members. The back board is connected with the main hull structure. The lower horizontal board is connected with a lower portion of the back board to extend in a horizontal direction. The vertical members are connected with the lower horizontal board, the upper horizontal board and the back board in at least a portion, such that a space formed by the upper horizontal board, the back board and the lower horizontal board is divided into a plurality of domains by the vertical members.
Here, each of the vertical members may extend in parallel to a longitudinal direction of the main hull structure, or may extend to intersect a longitudinal direction of the main hull structure.
Also, two of the vertical members may be used as inner vertical members to partition the space into three domains. In this case, the wave damping structure may further include a center front board provided to close a center domain of the three domains.
Also, other two of the vertical members may be connected with outer sides of the space as outer vertical members. In this case, the wave damping structure may further include a center front board provided to close a center domain of the three domains.
Also, a vertical direction hole may be provided for the lower horizontal board on both sides of the three domains. Also, a horizontal direction hole may be provided for each of the inner vertical members. In this case, it is desirable that the lower horizontal board is removed from a center domain of the three domains.
In another aspect of the present invention, a motion reduced floating structure includes a main hull structure and a wave damping structure connected with the main hull structure. The wave damping structure includes a back board, an upper horizontal board, a lower horizontal board, four vertical members and lids. The back board is connected with the main hull structure. The lower horizontal board is connected with a lower portion of the back board to extend in a horizontal direction and is under a seawater surface in case of mooring. The four vertical members are connected with the upper horizontal board, the lower horizontal board and the back board in at least a portion such that a space formed by the upper horizontal board, the back board and the lower horizontal board is divided into three domains by the vertical members. The lid is provided for each of both sides of the three domains to be closable in case of tow and openable in case of the mooring.
Here, a vertical direction hole is provided for the lower horizontal board on both sides of the three domains. Also, a horizontal direction hole is provided for each of the inner vertical members. In this case, the lower horizontal board is removed from a center domain of the three domains.
In another aspect of the present invention, a motion reduced floating structure includes a main hull structure and a wave damping structure connected with the main hull structure. The wave damping structure includes a back board connected with the main hull structure, an upper horizontal board, a lower horizontal board, two vertical members and a front vertical board. The lower horizontal board is connected with a lower portion of the back board to extend in a horizontal direction. The two vertical members are connected with the upper horizontal board, the lower horizontal board and the back board in at least a portion such that a domain is defined by the upper horizontal board, the back board and the lower horizontal board. The front vertical board is connected with the upper horizontal board, the lower horizontal board and each of the outer vertical members.
Also, a vertical direction hole may be provided for the lower horizontal board. Each of the vertical members may be openable in an outside direction.
In another aspect of the present invention, a motion reduced floating structure includes a main hull structure of a box type and a wave damping structure connected with the main hull structure. The wave damping structure includes a back board, a lower horizontal board, vertical members, and a vertical direction hole. The back board is connected used as one side board of the main hull structure. The lower horizontal board is formed by extending a lower horizontal board of the main hull structure and which is connected with a lower portion of the back board to extend in a horizontal direction. The vertical members are connected with the lower horizontal board and the back board. The vertical direction hole is provided for the lower horizontal board.
Also, the wave damping structure further may include an upper horizontal board which is formed by extending an upper horizontal board of the main hull structure. Each of the vertical members is connected with the upper horizontal board, in addition to the lower horizontal board and the back board in at least a portion such that a space formed by the upper horizontal board, the back board and the lower horizontal board is divided into a plurality of domains by the vertical members.